1. Field of the Invention
The present invention relates to a thin-film magnetic head having at least an induction-type magnetic transducer and a method of manufacturing the thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought with an increase in surface recording density of a hard disk drive. A composite thin-film magnetic head has been widely used, which is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase the recording density as one of the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the track width, that is, the width of a bottom pole and a top pole sandwiching the recording gap layer on the air bearing surface (medium facing surface) is reduced to the micron or submicron order. Semiconductor process techniques are employed to achieve the narrow track structure.
Reference is now made to FIG. 16A to FIG. 19A and FIG. 16B to FIG. 19B to describe an example of a method of manufacturing a composite thin-film magnetic head as a related-art method of manufacturing a thin-film magnetic head. FIG. 16A to FIG. 19A are cross sections each orthogonal to the air bearing surface. FIG. 16B to FIG. 19B are cross sections of a pole portion each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 16A and FIG. 16B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, on the bottom shield gap film 104, a pair of electrode layers 106 are formed. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top shield layer-cum-bottom pole layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 17A and FIG. 17B, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 18A and FIG. 18B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion-milling, using the top pole tip 110 as a mask. As shown in FIG. 18B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 110), the recording gap layer 109, and part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened.
Next, on the flattened insulating layer 111, a thin-film coil 112 of a first layer is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific pattern on the insulating layer 111 and the coil 112. Heat treatment is then performed to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a thin-film coil 114 of a second layer is formed. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is performed to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 19A and FIG. 19B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider including the above-described layers is performed to form an air bearing surface 118 of the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 20 is a top view of the thin-film magnetic head shown in FIG. 19A and FIG. 19B. The overcoat layer 117 and other insulating layers and insulating films are omitted in FIG. 20.
In FIG. 19A and FIG. 19B, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of the pole portion, that is, the portion of the two magnetic layers facing each other with the recording gap layer in between, between the air-bearing-surface-side end and the other end. The MR height is the length (height) of the MR element between the air-bearing-surface-side end and the other end. In FIG. 19A and FIG. 19B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the track width of the recording head (hereinafter called the recording track width). In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 19A and FIG. 19B is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coils 112 and 114 covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
In order to improve the performance of the thin-film magnetic head, it is important to precisely form throat height TH, MR height MR-H, apex angle xcex8, and recording track width P2W as shown in FIG. 19A or FIG. 19B.
To achieve high density recording, a reduction in track width and an increase in reproducing output are required for a recording head of a composite thin-film magnetic head as described above. A reduction in track width is required for a recording head, too. An improvement in high-frequency characteristic is required, too, for a recording head to cope with an increase in frequency of data to be written. To improve the high-frequency characteristic of a recording head, it is known that it is preferred to reduce the yoke length, that is, the length of the magnetic path made of the magnetic layers between the air-bearing-surface-side end and the other end.
One of the methods to reduce the yoke length may be to reduce the coil pitch. For example, the yoke length is required to be 20 to 10 xcexcm or less in order to implement a thin-film magnetic head that achieves recording density of 30 to 50 gigabits per square inch or more and performs desirable recording in a high-frequency band of 300 to 500 MHz or more. To obtain such a yoke length, the coil pitch is required to be 2.0 to 1.0 xcexcm or less, that is, 0.6 xcexcm, for example. If the coil pitch is 0.6 xcexcm, the line width of winding is 0.3 xcexcm and the space between windings is 0.3 xcexcm, for example.
In prior art a photoresist layer is used as an insulating layer for isolating windings of a coil from each other. The outermost end of the photoresist layer defines the throat height.
However, a rounded portion is formed near the outermost end of the photoresist layer since the photoresist has fluidity during its formation. As a result, the distance between the outermost end of the coil and the zero throat height position (the position of an end of the pole portion opposite to the air bearing surface) is increased in prior art, which is a major factor that prevents a reduction in yoke length. The reason will now be described in detail. Since the yoke length of a two-layer coil can be shorter than that of a single-layer coil, a two-layer coil is adopted to many of recording heads for high frequency application. However, in a related-art thin-film magnetic head, a photoresist film having a thickness of about 2 xcexcm is formed to cover the first layer of the coil for insulating the turns of the coil from each other after the first layer is formed. A rounded portion is formed as described above around the outermost end of the photoresist layer covering the first layer of the coil. A second layer of the coil is then formed on the photoresist layer. The second layer is required to be formed on a flat portion since it is impossible to etch the seed layer of the coil in the rounded portion near the outermost end of the photoresist layer, and the coil is thereby shorted.
Therefore, if the total coil thickness is 2 to 3 xcexcm, the thickness of the photoresist layer insulating the turns of the coil from each other is 2 xcexcm, and the apex angle is 45 to 55 degrees, for example, the yoke length is required to be 6 to 8 xcexcm which is twice as long as the distance between the outermost end of the coil and the neighborhood of the zero throat height position, that is, 3 to 4 xcexcm (the distance between the innermost end of the coil and the portion where the top and bottom pole layers are connected to each other is required to be 3 to 4 xcexcm, too), in addition to the length of the portion corresponding to the coil. This length of the portion other than the portion corresponding to the coil is one of the factors that prevent a reduction in yoke length.
Assuming that a two-layer eleven-turn coil whose line width is 1.5 xcexcm and the space between turns is 0.5 xcexcm is fabricated, for example, the portion of the yoke length corresponding to the coil 112 of the first layer is 11.5 xcexcm, if the first layer is made up of six turns and the second layer is made up of 5 turns, as shown in FIG. 19A and FIG. 19B. In addition to this length, the total of 6 to 8 xcexcm, that is, the distance between each of the outermost and innermost ends of the coil 112 of the first layer and each of ends of the photoresist layer 113 for insulating the coil 112, is required for the yoke length. The yoke length is therefore 17.5 to 19.5 xcexcm. In the present patent application, the yoke length is the length of a portion of the pole layer except the pole portion and the contact portions as indicated with L0 in FIG. 19A and FIG. 19B. As thus described, it is impossible in the prior art to reduce the yoke length, which prevents improvements in high frequency characteristic.
If a photoresist layer is used as an insulating layer for insulating turns of the coil from each other, problems further arising are that the photoresist tends to be deformed with time and that the photoresist layer is expanded due to heat generated around the coil when the thin-film magnetic head is used and the pole portion protrudes toward the recording medium.
In place of a resin insulation material (organic insulation material) such as a photoresist, the insulating layer for isolating the turns of the coil from each other may be made of an inorganic insulating material harder than a resin insulation material such as alumina or silicon dioxide.
However, if an insulating layer made of an inorganic insulation material is formed in a space between the turns of the coil having an aspect ratio of nearly 1 and a height of 0.5 to 1.0 xcexcm or more and a width of 2.0 xcexcm or less, for example, a problem is that the space between the turns is not completely filled with the inorganic insulation material and gaps called voids or keyholes are likely to be formed in the insulating layer. If such voids are formed in the insulating layer, a washing liquid or water goes into the voids during a number of cleaning steps using liquids performed after the formation of the coil until the magnetic head is completed. Such a liquid or water erodes the coil and the reliability of the head is reduced.
As disclosed in Published Unexamined Japanese Patent Application Hei 7-311912 (1995), after the coil is formed, a resist is applied in which the space between the turns of the coil is half buried, and then the remaining space between the turns is covered with an inorganic oxide. An insulating layer for isolating the turns of the coil from each other may be thus formed. In this case, deformation of the insulating layer with time and generation of voids in the insulating layer are prevented.
However, in this case, too, a rounded portion is formed near the outermost end of the resist layer formed first. It is therefore difficult to reduce the yoke length.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for reducing the yoke length and preventing generation of voids in the insulating layer for isolating the turns of the thin-film coil from each other.
A thin-film magnetic head of the invention comprises: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. At least one of the magnetic layers includes: a first portion located in a position that faces the at least part of the coil; and a second portion forming one of the pole portions and connected to a surface of the first portion that faces the coil. The at least part of the coil is placed on a side of the second portion. The head further comprises an insulating layer for insulating turns of the at least part of the coil from each other. The insulating layer includes: a first insulating film made of an insulating material that exhibits fluidity during formation and touching a layer to be a base of the at least part of the coil, the first insulating film being placed to fill at least part of the spaces between the turns of the at least part of the coil and between the second portion and the at least part of the coil; and a second insulating film made of an inorganic insulating material and placed to cover the first insulating film.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers.
The method of manufacturing the thin-film magnetic head includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; forming the coil such that the at least part of the coil is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. In at least one of the step of forming the first magnetic layer and the step of forming the second magnetic layer, at least one of the magnetic layers is formed to include: a first portion located in a position that faces the at least part of the coil; and a second portion forming one of the pole portions and connected to a surface of the first portion that faces the coil. In the step of forming the coil, the at least part of the coil is placed on a side of the second portion. The method further includes the step of forming an insulating layer for insulating turns of the at least part of the coil from each other. The step of forming the insulating layer includes the steps of: forming a first insulating film made of an insulating material that exhibits fluidity during formation such that the first insulating film touches a layer to be a base of the at least part of the coil and is placed to fill at least part of the spaces between the turns of the at least part of the coil and between the second portion and the at least part of the coil; and the step of forming a second insulating film made of an inorganic insulating material to cover the first insulating film.
According to the thin-film magnetic head or the manufacturing method of the invention, the at least part of the thin-film coil is placed on a side of the second portion, so that an end of the at least part of the coil is placed near an end of the second portion. The yoke length is thereby reduced. In the invention the insulating layer for insulating turns of the at least part of the coil from each other includes: the first insulating film made of an insulating material that exhibits fluidity during formation and touching a layer to be a base of the at least part of the coil, the first insulating film being placed to fill at least part of the spaces between the turns of the at least part of the coil and between the second portion and the at least part of the coil; and the second insulating film made of an inorganic insulating material and placed to cover the first insulating film. As a result, generation of voids in the insulating layer for insulating turns of the coil from each other is prevented.
According to the head or the method of the invention, the first insulating film may be made of an organic insulating material or may be a spin-on-glass film.
According to the head or the method, a surface of the second insulating film opposite to the first insulating film may be flattened.
According to the head or the method, the first insulating film may be formed to cover at least part of the thin-film coil or may be formed such that the part of the spaces is filled with the first insulating film.
According to the method of the invention, the step of forming the first insulating layer may include the steps of: forming a film made of the insulating material that exhibits fluidity during formation to cover the at least part of the coil; and removing the film placed on top of the at least part of the coil through etch back.
Other and further objects, features and advantages of the invention will appear more fully from the following description.